1. Field of the Invention
The subject invention generally pertains to barrel locks and more specifically to a barrel lock actuated by a ball and mandrel.
2. Description of Related Art
Barrel locks are typically used for preventing unauthorized personnel from tampering with public utility devices such as valves and meters for gas, water and electricity.
Many barrel locks comprise a shank with a head at one end and a locking mechanism at the opposite end. The locking mechanism typically includes two or more balls that can be forced to protrude radially outward beyond the outside diameter of the shank. A mandrel inside the shank, and actuated by a separate key, forces the balls outward or allows the balls to retract depending on which direction the mandrel is rotated.
To lock a utilities device, the device requires a feature for receiving the barrel lock. A gas valve, for instance, may include a tab extending from the valve's housing and another one extending from the valve's handle. Each tab would have a hole so that when the handle is rotated to a closed position, the holes become aligned to receive the shank of the barrel lock, which inhibits the handle from rotating the valve back open.
To prevent someone from simply withdrawing the shank from within the holes, the end of the shank with the locking mechanism protrudes beyond the two tabs, and a close-fitting, cap-like retainer is placed over that end of the shank and locked there. In order to place the retainer on the end of the shank, the balls first need to be retracted within the shank, due to the close fitting clearance between the outside diameter of the shank and the inside diameter of the retainer. Once the retainer is on the end of the shank, the key is used to rotate the mandrel, which forces the balls outward to extend into an annular groove that is inside the retainer, thereby locking the retainer to the shank and capturing the two tabs between the retainer and the head of the barrel lock.
There is a problem, however, with such barrel locks. There are a wide variety of utilities devices but not nearly as many different size barrel locks, so in some applications, the barrel lock may not fit as tightly as it should. Excessive axial clearance may exist underneath the shank's head or between one of the valve's tabs and the retainer. If sufficiently large, such clearance could allow a pry bar to be inserted underneath the head or the retainer to force the barrel lock apart.
To address this problem, some retainers have two axially spaced apart annular grooves, so the axial distance between the head and the retainer is determined by which groove is selected to receive the balls of the locking mechanism. Although this provides some adjustability, the discrete steps of adjustment are far too crude to effectively solve the problem. Consequently, a need still exists for an adjustable barrel lock that can tightly fit a wide variety of devices.